title: Polyadenylation linked to transcription termination directs the processing of snoRNA precursors in yeast.
abstract: Transcription termination by RNA polymerase II is coupled to transcript 3' end formation. A large cleavage and polyadenylation complex containing the major poly(A) polymerase Pap1 produces mRNA 3' ends, whereas those of nonpolyadenylated snoRNAs in yeast are formed either by endonucleolytic cleavage or by termination, followed by trimming by the nuclear exosome. We show that synthesis of independently transcribed snoRNAs involves default polyadenylation of two classes of precursors derived from termination at a main Nrd1/Nab3-dependent site or a "fail-safe" mRNA-like signal. Poly(A) tails are added by Pap1 to both forms, whereas the alternative poly(A) polymerase Tfr4 adenylates major precursors and processing intermediates to facilitate further polyadenylation by Pap1 and maturation by the exosome/Rrp6. A more important role of Trf4/TRAMP, however, is to enhance Nrd1 association with snoRNA genes. We propose a model in which polyadenylation of pre-snoRNAs is a key event linking their transcription termination, 3' end processing, and degradation.
authors.affiliation: Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland.
authors.forename: Pawel
authors.initials: P
authors.lastname: Grzechnik
authors.forename: Joanna
authors.initials: J
authors.lastname: Kufel
mesh_terms: D004259:DNA-Directed DNA Polymerase / Q000502:physiology; D005095:Exoribonucleases / Q000235:genetics; D063326:Exosome Multienzyme Ribonuclease Complex; D008957:Models, Genetic; D009687:Nuclear Proteins / Q000378:metabolism; D000073718:Pancreatitis-Associated Proteins; D026723:Polyadenylation / Q000502:physiology*; D011062:Polynucleotide Adenylyltransferase / Q000502:physiology; D012322:RNA Precursors / Q000378:metabolism*; D020537:RNA, Small Nucleolar / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D012261:Ribonucleoproteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D014158:Transcription, Genetic / Q000502:physiology*
chemical_list: C090564:NAB3 protein, S cerevisiae; C491211:NRD1 protein, S cerevisiae; D009687:Nuclear Proteins; D000073718:Pancreatitis-Associated Proteins; C000612141:REG3A protein, human; D012322:RNA Precursors; D020537:RNA, Small Nucleolar; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D029701:Saccharomyces cerevisiae Proteins; C429559:PAP1 protein, S cerevisiae; D011062:Polynucleotide Adenylyltransferase; D004259:DNA-Directed DNA Polymerase; C487545:PAP2 protein, S cerevisiae; D005095:Exoribonucleases; D063326:Exosome Multienzyme Ribonuclease Complex; C112610:RRP6 protein, S cerevisiae